(a) Field of the Invention
The present invention relates to an electrostatic imaging device such as a printer and a facsimile machine using an electrophotographic technique, and more particularly, to an electrostatic imaging device capable of obtaining a high-quality image regardless of the variation in ambient conditions. The present invention also relates to a method for forming an image in the electrostatic imaging device.
(b) Description of the Related Art
Conventional electrostatic imaging devices are described in JP-A-6(1994)-161294 (first publication) and JP-A-5-313515 (second publication), for example. In the electrostatic imaging device described in the first publication, a driving voltage calculator calculates a driving voltage based on the temperature data from a thermal sensor and the humidity data from a humidity sensor with reference to data stored in a ROM. An I/O controller transmits the calculated driving voltage data to a driver of an electrification unit, to control the transcribing potential to be supplied from the electrification unit to the transcribing roller based on the detected temperature and the detected humidity.
In the electrostatic imaging device described in the second publication, when the temperature and humidity within the device are detected by the temperature and humidity sensors and supplied to a CPU, the CPU judges which range in the first table data stored in the memory the detected temperature and the humidity reside. Then, the CPU reads the transcription current data and the voltage control data for removing an electric charge corresponding to the toner species of the transcribed toner image with reference to the second table data stored in the memory, thereby selecting the transcription current and the voltage control data for removing the electric charge.
As described above, the electrostatic imaging devices described in the above first and second publications determine a suitable transcription current for the ambient conditions based on the detected temperature and humidity. Accordingly, it is necessary in the prior art to examine the locations for the thermal and humidity sensors before fabrication of the device and determine the most suitable ambient conditions for transcription. This increases the number of the steps for designing the electrostatic imaging device and decreases the available design choices for the device.